Superabsorbent polymers (SAPs) are generally capable of absorbing and retaining amounts of aqueous fluids equivalent to many times their own weight. After absorption of an aqueous solution, swollen SAP particles become very soft and they may be deformed easily. Upon deformation, the void spaces between the SAP particles may be blocked which may increase the flow resistance for liquids. This is generally referred as “gel-blocking”.
SAP particles may include a partially neutralized lightly cross-linked polyacrylic acid network, which is a hydrophilic network and permits swelling of the network once submerged in water or any aqueous solutions. The cross links between the polymeric chains may assure that the SAPs do not dissolve in water. SAPs applied in form of small particles, such as fibers or granules.
One way to reduce gel-blocking is to make the SAP particles stiffer, which enables the SAP particles to retain their original shape thus creating or maintaining void spaces between the particles.
Low swollen gel strength and the adverse effects of gel-blocking are two major challenges of the superabsorbents. Therefore, there is a need in the art to provide SAP particles with a high degree of surface cross-linking in order to avoid gel-blocking and to have a high swollen gel strength.